German Foreign Minister Guido Westerwelle on Wednesday said images of demonstrators in Istanbul being chased down by riot police were "disturbing" and warned that the Turkish government was sending the "wrong message".

Reacting after Turkish security forces retook control of Taksim Square, the flashpoint of nationwide unrest, Westerwelle urged Ankara to respect the rights of free speech and assembly.

An uneasy calm returned to Istanbul's protest square early Wednesday after running clashes between riot police and protesters, as Turkish leader Recep Tayyip Erdogan vowed zero tolerance for the mass demos.

Hours earlier, Taksim Square had resembled a battle scene, swathed in acrid smoke as police dispersed tens of thousands of protesters chanting "Erdogan, resign!" and "Resistance!" on the worst night of violence in 12 days of nationwide unrest.

A small Istanbul park whose conservation fight sparked mass protests will not be turned into a shopping mall, the city's mayor assured protesters Friday, but insisted the site's controversial redevelopment would go ahead.

"We are definitely not thinking of building a shopping mall there, no hotel or residence either. It can be... a city museum or an exhibition center," Istanbul mayor Kadir Topbas told reporters.

Thousands of angry Turks took to the streets on Saturday to join mass anti-government protests, defying Prime Minister Recep Tayyip Erdogan's call to end the worst civil unrest of his decade-long rule.

From the early morning, protesters began arriving in Istanbul's Taksim Square with food and blankets to settle in for a weekend of demonstrations, adding to the growing tent city in nearby Gezi Park.

Turkish Prime Minister Recep Tayyip Erdogan called for an immediate end to mass protests against his rule Friday, but urged supporters to "go home" after they staged a major show of strength welcoming him back from an overseas trip.

Waving Turkish flags and chanting "We will die for you, Erdogan" and "Let us go crush them all", supporters of the premier's Justice and Development Party (AKP) displayed their support after keeping largely silent during seven days of violent anti-government demonstrations across the country.

A group representing Turkey's protesters on Wednesday urged the government to fire the police chiefs of Istanbul and Ankara and other cities where security forces have violently cracked down on political protests as Turkish police fired tear gas and water cannon to disperse crowds who joined the mass demonstrations.

"We demand that those police chiefs... who are responsible for violence and pressure are dismissed," a spokesman for the protesters told reporters as he read a list of demands after meeting with Deputy Prime Minister Bulent Arinc in Ankara.

Thousands of people were on Sunday occupying Istanbul's Taksim Square, the epicenter of the worst demonstrations in a decade against Turkey's Islamist-rooted government which have seen almost 1,700 people detained and scores wounded.

A sea of protesters from across Turkey's political spectrum were camping out in the iconic square, chanting "Government, Resign!" and "Istanbul is ours, Taksim is ours!" as they celebrated after the police pulled out of the site on Saturday.

Riot police fired tear gas at hundreds of demonstrators on Friday, injuring at least a dozen people, in a bid to break up a four-day protest against a major construction project in Istanbul's iconic Taksim Square.

Several of the wounded were left lying on the ground unconscious after they were hit with large quantities of tear gas and pepper spray, while two people were hospitalized with injuries to the head, an Agence France Presse photographer witnessed.

Less than four months before the IOC vote, the three cities vying for the 2020 Olympics took their campaign to a key international audience on Thursday — with each claiming to be the safest and most financially secure choice at a time of global uncertainty.

Officials from Istanbul, Madrid and Tokyo made presentations to the SportAccord conference in St. Petersburg, their first chance to pitch their bids in public to sports and Olympic officials.

Turkish police have rounded up 12 people suspected of ties to a "terrorist organization" in a string of raids across Turkey, the governor of the southern city of Adana said on Thursday.

Local media reported the suspects were affiliated with al-Qaida and the jihadist al-Nusra Front battling the regime of Bashar Assad in Syria.